E-7

E-7

THEORY OF OPERATION

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CHOPPER TECHNOLOGY

FUNDAMENTALS

The new era of welding machines such as the Commander 500, employ a technology whereby a DC source is turned on and off (chopped up) at high speed, then smoothed through an inductor to control an arc.

Hence the name “Chopper.” The biggest advantage of chopper technology is the high-speed control of the arc, similar to the inverter machines. A block diagram for this is as follows:

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EXTERNAL DC

SOLID STATE

INDUCTOR

ARC

SOURCE

SWITCH

AND DIODE

 

ARC

CONTROL

In this system, the engine drives a three-phase alter-

turning the switch on and off, current in the inductor

nator, which generates power that is rectified and

and the arc can be controlled. The following diagram

filtered to produce about 85VDC[?]. The current is

depicts the current flow in the system when the switch

applied through a solid state switch to an inductor. By

is open and closed.s

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SWITCH

70-80VDC

DIODE

INDUCTOR

ARC

CURRENT WITH SWITCH OPEN

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CURRENT WITH SWITCH CLOSED

When the switch is closed, current is applied through

varying the ratio of on time versus off time of the switch

the inductor to the arc. When the switch opens, current

(Duty Cycle),

the current applied to the arc is con-

stored in the inductor sustains flow in the arc and

trolled. This

is the basis for Chopper Technology:

through the diode. The repetition rate of switch closure

Controlling the switch in such a way as to produce

is 20Khz, which allows ultra-fast control of the arc. By

superior welding.

COMMANDER 500

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Lincoln Electric SVM153-A Chopper Technology Fundamentals, External DC Solid State Inductor ARC Source Switch Diode
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